In 1963, a Government Decree ordained the preparation of an investment programme, the design documentation of which was finalised in 1966. The investment target outlined Újpest vasútállomás and Kispest Vörös Csillag Traktorgyár as terminals of the line. This investment programme was passed in 1968, and the construction started in June 1970, by sinking the shaft at Kun Béla tér.
Line alignment and station location have been modified in the course of engineering/design, and the line in its actual state - i.e. Kőbánya-Kispest - Újpest - was completed in 1990. Finalisation of this line is still not envisaged, consequently, no direct connection with the housing estate "Káposztásmegyer" and the railway station Szob and Fót, as well as with the northern depot are planned.
Take-over of various line sections took place at the following dates:
- December 31, 1976: Deák tér - Nagyvárad tér.
- March 29, 1980: Nagyvárad tér - Kőbánya Kispest.
- December 30, 1981: Deák tér - Lehel tér.
- November 5, 1984: Lehel tér - Árpád híd.
- December 14, 1990: Árpád híd - Újpest központ.
The trains on this North-South line and the whole Metro line operate with an automatic train control system supplied by the French MATRA Company, which ensures an extremely high level of safety despite of a single-driver operation.